1. Field of the Invention
The present invention relates to a nickel oxide film for a bolometer and a method for manufacturing thereof, and an infrared detector using the nickel oxide film.
2. Description of the Related Art
A bolometer is a kind of an infrared detector. The bolometer may absorb incident infrared rays to cause a change in temperature, and then detect the incident infrared rays by measuring a change in electric resistance generated by the temperature change. There are a first method for changing a structure of the bolometer and a second method for improving properties of a bolometer material to improve a performance of the bolometer. In this case, the properties for the bolometer material required in the second method are a high temperature coefficient of resistance (TCR), a low 1/f noise, and an ohmic resistance with low contact resistance between a bolometer sensing material and a bolometer leg. Further, compatibility with an IC process, simplification of a process, low cost, and, stable electric characteristics and reproducibility should be satisfied.
The bolometer materials recently used are amorphous silicon, metal thin films, metal oxide films, etc. Titanium, nickel, nickel-iron, and the like are used as the metal thin films. The titanium has a small resistivity of 42 uΩ-cm, a small TCR value of 0.4%/K, and a small 1/f noise value. The nickel has a resistivity of 6.93 uΩ-cm and a TCR value of 0.68%/K. The metal thin film has a small resistivity, a small TCR value, and a small noise value. Such a small TCR value has a problem that it deteriorates the responsibility property of the bolometer.
Metal oxide films tend to have a relatively high TCR value and a relatively low noise value. Among them, a vanadium oxide film has a high TCR value around −2.0%/K, electrical resistance of 100 kΩ, and a low 1/f noise value. However, the metal oxide films have problems in that it is difficult to fabricate them with high reproducibility due to the existence of materials being in metastable states, thereby making it difficult to change a resistance value and to obtain stable electric characteristics.
Furthermore, although the amorphous silicon has a TCR value around −2.0%/K and a resistivity greater than 100 Ω-cm, it has a problem that it has a relatively higher noise value than that of other materials. In addition, the amorphous silicon and the vanadium oxide film have problems in that they use expensive equipment and a complicated process.